1. Field of the Invention
This invention relates generally to devices and methods for facilitating intravenous access, and in particular to such devices and methods utilizing various combinations of vacuum, heat and tactile stimulation to dilate peripheral veins and thereby to facilitate their identification for blood sampling or cannulation. Other applications of the present invention, however, are also possible, and are within the scope of what the inventor regards as his invention.
2. Related Background Art
Peripheral intravenous access plays an integral role in treatment of patients with both critical and non-critical conditions. It is routinely accomplished by application of a tourniquet to an extremity with enough pressure to occlude venous drainage, but not arterial inflow, thereby causing dilation of veins distal to the tourniquet. Once a dilated vessel is identified, a cannula is inserted percutaneously. Not infrequently, underlying physiologic states including, but not limited to, dehydration, shock from blood loss or redistribution of blood volume, hypothermia, and even anxiety cause peripheral vasoconstriction by neuroendocrine pathways. This vasoconstriction often impedes the normal venous dilation when a tourniquet is applied, making intravenous access problematic. At this point, medical specialists will often apply heat or tactile stimulation, or place the extremity lower than the heart in an attempt to improve peripheral blood flow and overcome vasoconstriction. More central access, with its greater inherent risk to the patient, is often needed if these efforts fail.
Various efforts have been made to ameliorate these problems. U.S. Pat. No. 4,299,219 (Norris, Jr.) relates to a device to dilate peripheral veins at the site of application of the device. Suction from the device is created by an operator-activated plunger. The utility of the device appears to be limited by at least two factors: (1) its usefulness presupposes that a target vein can be identified prior to application of the device; and (2) the device only causes a small area of venodilation, which will rapidly collapse on needle entry.
U.S. Pat. No. 4,747,409 (Silen) relates to a sleeve with heating elements used to enwrap a distal extremity for the purpose of warming, thereby enhancing arterial blood flow. This device would seem to have limited ability to counteract vasoconstriction on the venous side of the circulation.
U.S. Pat. No. 5,074,285 (Wright) relates to one of a number of known devices for applying a thermal environment to an extremity in the hope of achieving various therapeutic effects. An extremity is placed within a stocking that has pockets placed along its length. Thermal elements are then placed in one or more of the pockets, with the intent of applying heat or cold at one or more specified sites along the extremity. This device also incorporates a series of compartments placed along the length of a tubular body that encases the extremity and stocking with the purpose of applying a pressure gradient along the length of the tubular body. The sequenced pressure gradient is used primarily in treating lymphatic or venous stasis problems in extremities requiring thermal therapy.
U.S. Pat. No. 5,441,477 (Hargest) relates to an apparatus combining electrotherapy and the massaging action of a thermally energized fluidized bed for treating injured extremities. (Other patents also relate to the use of a fluidized bed for massaging a part of a body, with or without heating or cooling, e.g., U.S. Pat. No. 4,214,576 (Henley).)
U.S. Pat. No. 5,683,438 (Grahn) relates to a device that combines a heat source with a sustained vacuum to dilate superficial capillary beds with the intent of treating hypothermia.
It is an object of the present invention to provide a device and method that enable reliable dilation of veins and their subsequent identification and access for venipuncture or the like.
According to one aspect of the present invention, this object is attained by providing a device which includes a chamber having an interior for receiving a portion of a body, and having at least one inlet for admitting a fluid into the chamber. A fluid supply is connected to the inlet to enable the fluid to be admitted into the chamber. A heater is positioned so as to be able to heat the fluid being supplied to the chamber by the fluid supply. A suction source is connected to the chamber in such manner as to enable application of suction to the interior of the chamber. The chamber may contain particulate matter such that supply of the fluid into the chamber produces a fluidized bed. The chamber preferably contains a partition or sleeve that divides the chamber into two portions, one of which receives an extremity of a patient""s body while the other receives the fluid.
Another aspect of the invention is a method of vasodilation, in which a portion of a body is heated (for example, by means of a fluidized bed), and a vacuum is applied to the portion of the body for a period of time after performance of the heating step. In one embodiment, the heating step may also include massaging of the portion of the body.
These and other objects, features and advantages of the present invention will be more fully appreciated from a consideration of the following detailed description of the preferred embodiments, taken together with the accompanying drawings.